Solvent-free temperature gradient melt formation of efficient visible-to-UV photon upconversion organic films with subsolar threshold and over 100 h photostability in air

Abstract

Completely solvent-free “green” formation of bicomponent organic polycrystalline films for efficient visible-to-ultraviolet photon upconversion (UV-UC) were achieved by temperature-gradient solidification from the melt. The UV-UC film formed under optimal conditions exhibited an ultralow excitation threshold (0.3 suns, AM1.5 spectrum with a 413 nm long-pass filter) and a record-long photostability (>100 h) in air.